Abstract
Among several analytical models to describe the behavior of reinforced concrete (RC) and longitudinally prestressed concrete (LPC) beams under torsion, the Modified Variable Angle Truss Model (MVATM) is particularly efficient to capture the behavioral states of the member until failure and agree well with experimental results. This article aims to extend the MVATM to cover transversally prestressed concrete (TPC) beams under torsion. The changes in the formulation and calculation procedure of the original VATM, in order to include the influence of transversal prestress, are presented. The extended MAVTM is then used to compute the global response of LPC and TPC beams under torsion with similar total prestress reinforcement ratios, namely the torque–twist curves. The obtained predictions are then compared and discussed. It is shown that for the ultimate loading, transversal prestress constitutes also an effective solution to improve the behavior of the beams under torsion. However, transversal prestress is less effective to delay the cracked state. Finally, it is also shown that when prestress is distributed in both longitudinal and transversal direction, the global response of the beams under torsion is further improved, namely the resistance torque and the torsional stiffness in the cracked state.
Highlights
Several theoretical models have been developed to predict the behavior of Reinforced Concrete (RC) beams under torsion
Designs 2018, 2, 12 because Variable Angle Truss Model (VATM) assumes that the response of the beam starts from the cracked state and because it neglects the influence of the concrete core for plain beams
Some theoretical results obtained with Modified Variable Angle Truss Model (MVATM) extended to transversally prestressed concrete (TPC) beams are used to compare the global behavior under torsion of TPC, Longitudinally Prestressed Concrete (LPC) and LTPC beams
Summary
Several theoretical models have been developed to predict the behavior of Reinforced Concrete (RC) beams under torsion. Designs 2018, 2, 12 because VATM assumes that the response of the beam starts from the cracked state and because it neglects the influence of the concrete core for plain beams To solve this issue, Jeng and Hsu in 2009 [12], Jeng et al in 2010 [13] and Jeng in 2015 [14] proposed the Softened Membrane Model for Torsion (SMMT) to model RC and LPC beams. Bernardo et al in 2012 [16] and in 2015 [17] proposed new developments of the original VATM, namely the Modified VATM (MVATM) and the Generalized Softened VATM (GSVATM) These models are able to predict well the entire T–θ curves of RC and LPC beams under torsion [18,19,20].
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